Alaska’s First Fossil Ichthyosaur Found With Last Meal Still in Its Gut

New insights into life in the ancient oceans are emerging from a huge fossil found in a remote reach of northern Alaska — the largest and most complete specimen of an ichthyosaur yet found in the region.

Ichthyosaurs in some ways resembled modern porpoises and whales, having to surface to breathe and giving birth to live young.

But they bear no relation to today’s aquatic mammals; instead, they were marine reptiles, and the largest of them — including the group that the Alaska specimen belonged to — were some of the biggest animals that ever swam.

“Ichthyosaurs were amazing animals,” said Dr. Pat Druckenmiller, earth sciences curator at the University of Alaska’s Museum of the North, in a press statement.

Shastasaurid ichthyosaur
An artist’s rendering shows Shonisaurus popularis, a shastasaurid similar to the ichthyosaur recently identified from an Alaskan fossil. (Courtesy Dmitry Bogdanov)

“The Alaskan specimen is a type called a shastasaurid, which includes the largest marine reptiles to have ever lived – some rivaled the size of living blue whales.”

The fossil dates back some 210 million years, when most of the planet’s land was locked in two supercontinents, and the rest — including what’s now Alaska — was covered with water.

“This particular animal died during the Triassic Period and settled to the floor of the sea that used to occupy the place where Alaska is now located,” Druckenmiller explained.

“Since then, the bottom of that sea has been pushed up.”

Ichthyosaurs ruled these ancient seas as a diverse group of marine predators, as evidenced by even more fossils of found inside the Alaskan specimen.

A close-up view of the ichthyosaur’s gut contents show iridescent fragments from an ammonite shell and bluish-gray bone fragments from a fish. (UAFMN)

Its innards were found to contain fragments of fish bone and the shells of ammonites — the undigested remains of its final prey.

“We found the last meals that this animal ate,” Druckenmiller said.

“Finding gut contents in an ichthyosaur of this age is very rare and provides valuable insights into the diet and ecology of Triassic ichthyosaurs.

“This is especially interesting considering that some of these large animals may have lacked teeth.”

In addition to being the largest and best-preserved of its kind, as well as the northernmost specimen from the Triassic, the fossil is also the first to have been found in Alaska — though it took several decades to earn that title. [Read about another recent find by Druckenmiller’s team: “Thousands of Dinosaur Tracks Discovered Along Alaska’s Yukon River“]

The fossil was first identified in 1950 by geologists surveying what’s now the National Petroleum Reserve-Alaska.

“We knew what it was when we found it,” said Carl Benson, one of the scientists who was on the expedition, in a statement.

“We talked about it in the tent that night and during the remainder of the field season.”

A photo and interpretation of the ichthyosaur fossil. Note the dotted area left of center, indicating the animal’s gut contents. (Druckenmiller et al./JVP)

But the animal measured some 10 meters in life, and the best-preserved portion of its fossil was nearly half that size, far too large to pack out of the wilderness.

It wasn’t until 2002 that the remains had been excavated and could be airlifted by U.S. Army helicopter to Fairbanks.

Five years later, Druckenmiller and his colleagues set about removing rock from around the fossil and analyzing its contents. [See another recent Alaska fossil find: “Ostrich-Like Dinosaur Discovered in Alaska“]

“When we brought it out of storage, we began cleaning up the skeleton and could see the bones clearly for the first time.”

Druckenmiller and his colleagues report the find in the Journal of Vertebrate Paleontology.

Druckenmiller, P., Kelley, N., Whalen, M., Mcroberts, C., & Carter, J. (2014). An Upper Triassic (Norian) ichthyosaur (Reptilia, Ichthyopterygia) from northern Alaska and dietary insight based on gut contents Journal of Vertebrate Paleontology, 34 (6), 1460-1465 DOI: 10.1080/02724634.2014.866573

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  1. The D

    It’s almost hard to believe that anything could survive 200+ million years and still be so in tact. Fascinating.